Enhanced recovery methods are commonly used to increase the amount of hydrocarbons that can be recovered from a reservoir. One enhanced recovery method includes a miscible displacement process. In a miscible displacement process, a displacement fluid (e.g., carbon dioxide with light hydrocarbons) is selected that is miscible with the hydrocarbons to be recovered from the reservoir. The displacement fluid is injected into the reservoir (e.g., through an injection well) and forms a miscible solution with the hydrocarbons. Additional displacement fluid is injected into the reservoir to drive the miscible solution with the hydrocarbons out of the reservoir (e.g., through a recovery well).
Two important parameters in a miscible displacement process include the minimum miscible pressure and the fracture pressure. The minimum miscible pressure is the lowest pressure at which the displacement fluid and the hydrocarbons can become a miscible solution. The fracture pressure is the pressure at which damage (e.g., structural damage) of the reservoir may occur. Accordingly, to use a particular miscible displacement process at a particular reservoir, the minimum miscible pressure should be lower than the fracture pressure. This enables the miscible solution to be formed and driven from the reservoir without damaging the reservoir. Additionally, it may be preferable to operate a miscible displacement process at a pressure above the minimum miscible pressure to prevent low miscibility, unstable displacements, fingerings, and poor recovery. Therefore, it may be desirable to lower a minimum miscible pressure of a displacement fluid.